On my rooted device, I have following tools installed:

1. Terminal Emulator
2. BusyBox Free

On Terminal Emulator, su command successfully changes user to a real root:

root@hwH30-U10:/ # id -u
uid=0(root) gid=0(root)

Then I remount /system as R/W:

root@hwH30-U10:/ # mount | grep system
/emmc@android /system ext4 rw,realtime,noauto_da_alloc,commit=1,data=ordered 0 0

Then I even:

root@hwH30-U10:/ # chmod 777 /system

But I can not change any thing e.g. permissions or contents of /system original files like /system/build.prop!

I am sure that permissions and mounts are OK because I can create a new file, /system/tmp.prop, change it's contents and permissions by Terminal Emulator.

I really have no idea why these operations are not permitted while in Linux point of view, all things are OK for root to do these changes!

Is there any hard-coded further protection inside Android e.g. in kernel?

How to figure out this, please?

On my rooted device running Android 4.2.2, I have following tools installed:

1. Terminal Emulator
2. BusyBox Free

On Terminal Emulator, su command successfully changes user to a real root:

root@hwH30-U10:/ # id -u
uid=0(root) gid=0(root)

Then I remount /system as R/W:

root@hwH30-U10:/ # mount | grep system
/emmc@android /system ext4 rw,realtime,noauto_da_alloc,commit=1,data=ordered 0 0

Then I even:

root@hwH30-U10:/ # chmod 777 /system

But I can not change any thing e.g. permissions or contents of /system original files like /system/build.prop!

I am sure that permissions and mounts are OK because I can create a new file, /system/tmp.prop, change it's contents and permissions by Terminal Emulator.

I really have no idea why these operations are not permitted while in Linux point of view, all things are OK for root to do these changes!

Is there any hard-coded further protection inside Android e.g. in kernel?

How to figure out this, please?